The instant invention is directed toward an ablation catheter and sheath incorporating wire rail system. The catheter may have a combination of rigid and flexible components to orient an ablation electrode at the distal tip toward the target tissue. The wire rail acts to guide an ablation tip along the tissue to aid in the formation of spot or continuous linear lesions on a trabecular surface, e.g., in the right atrium along the isthmus between the ostium of the inferior vena cava and the tricuspid valve.